Thank you for the insightful information Alien.
Our perception on reliability is jaundiced by the penalties that are usually attached to any reliability issues. So what we see is reliability issues affecting the start of the race (drivers suffering huge position drops) rather than during the race where a DNF is barely noticed.
In racing there is a well worn adage where if a car finishes a race, it is too reliable and thus too heavy. So mass must be removed. The opposite is that if the car breaks, something is too light, and weight must be added. In racing, finding this balance is where a lot of money and resources are spent. Even where the entire car may be underweight, being able to relocate mass can yeild noticeable performance gains.
Every nut, bolt, part is subjected to a comprehensive weight and stress analysis, in an effort to understand what stresses each part is subjected to, and hot to make it strong enough, but as light as possible. Computers have become a huge part of this process, and by running (for example) a Finite Element Structural and Fatigue Analysis do engineers come closer to finding that magic sweet spot.
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTvHjOToYE6P8W5CqiFU3vshFJVxUSZ9jobXuixh0JZAHX5tuR5We did not have these kinds of tools a couple of decades ago, and the ability to make such detailed analysis has contributed heavily to performance and reliability gains.
But this is racing, and when you are locked in a battle worth many millions of dollars and the difference in performance between teams is so minuscule, each part is stressed to the absolute maximum. In today's racing, reliability is determined by each team's willingness to push the boundaries.
Here's a little true story that may assist in understanding. NASCAR has three tiers, and occasionally drivers in the top tier would race in the 2nd tier for money or just to learn the track. And they would usually win. That is because the regular second tier drivers are running for a championship, and thus their cars are not as stressed. But the ringers could run at the limit because they were in it to either win or blow up.